A conventional impact wrench is mainly used for loosening or tightening a screw. The common hand impact wrench is a manual impact wrench. One end of the main body is formed with two pivot lugs. A sleeve having a hollow cylinder is provided between the two pivot lugs. The sleeve includes a spring and a reversing member therein. One end of the reversing member is accommodated in the sleeve and leans against the spring. The other end of the reversing member extends out to form a driving head. The peripheral surface of the reversing member is provided with a reversing portion on each of the two opposite sides. The reversing portion has a forward groove and a reverse groove with opposite slopes. The forward groove and the reverse groove are communicated with a turning groove. Two positioning posts are inserted through the pivot lugs, the sleeve and the reversing member in order. The distal ends of the positioning posts are accommodated in the reversing portions of the reversing member.
The above-mentioned conventional structure mainly uses the driving head to engage with a tool part, such as a sleeve, to apply an external force to the hammering surface of the sleeve by means of a hand tool, such as a hammer. The tool part engaged with the driving head is to loosen or tighten the screw through an instantaneous displacement force.
However, these components are complicated, and the user needs to use the hammer to hammer the hammering surface of the sleeve. This is troublesome and inconvenient for operation and use. Besides, since the torque value per hammering is small and fixed, therefore, it takes a lot of time to loosen or tighten the screw. Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve these problems.